This project maintains and expands a National HIV Behavioral Surveillance (NHBS) system that provides relevant, timely, and high-quality data on risk and prevention behaviors of men who have sex with men, injection drug users, and high-risk heterosexuals to help direct and evaluate local and national HIV prevention efforts. In the absence of an effective vaccine against HIV, reducing known behavioral risk factors for HIV infection is essential for reducing HIV transmission. HIV behavioral surveillance data can be used to target prevention efforts to help reduce identified risk behaviors in populations at greatest risk for HIV infection. Since 1994, state and local health departments have been directed to use a community planning process to allocate federal HIV prevention resources to populations in greatest need. A behavioral surveillance system that provides relevant, timely, and high-quality risk and prevention behavior data is needed to help community planning groups and state and local health departments construct evidence-based plans to appropriately direct local HIV prevention efforts. Although HIV behavioral surveillance data cannot be used to evaluate the efficacy of specific interventions, behavioral surveillance data is important for evaluating whether prevention efforts within a community are reaching important population segments and meeting local and national goals for HIV prevention. For several important populations, objectives within the Centers for Diseases Control and Prevention's (CDC) HIV/AIDS Strategic Plan specify reducing the proportion of persons who are at high risk for acquiring HIV and increasing the proportion of high-risk persons who routinely access voluntary counseling and testing and other HIV prevention services. Ongoing, systematic collection, interpretation, and analysis of behavioral data are needed to identify baseline risk and prevention-service-utilization outcomes, and to quantify progress towards meeting the Strategic Plan's objectives. For those populations that are identified with unmet prevention needs, behavioral surveillance data can be used at local, state, and federal levels to help improve or redirect prevention efforts, or to obtain additional prevention resources. The primary National HIV Behavioral Surveillance (NHBS) objectives include: 1) Estimating the prevalence of and trends in specific sexual and drug-use behaviors known to be associated with HIV, sexually transmitted diseases (STDs), and hepatitis B and C infection; 2) Estimating demographic, social, and behavioral correlates of behavioral outcomes of interest; 3) Assessing HIV, hepatitis B, and hepatitis C sero-prevalence; 4) Estimating the prevalence and trends in HIV testing behaviors, and exposure to and utilization of HIV/STD/hepatitis prevention services funded by CDC and state and local health departments; and, 5) Characterizing prevention service gaps and missed opportunities for prevention.